This invention relates to a monolithic silicon mass flow control structure, particularly to a mass flow control structure comprising a flow-sensing module, a thermal buckling valve, and a distributary module all made by micro electromechanical technology, wherein at least one micro flow measurer and a micro valve are integrated and constructed on a single chip for mass flow control.
A conventional flow-measuring module is usually made by forming a flow channel with tubing technology, winding a pair of wire thermistors on outer tube wall, and hand operation spot welding to control difference between thermistors precisely. Therefore, when a fluid is flowing through the channel, the difference in thermistors can be used for calculation of the flow rate.
As most parts of the module must be made by handwork, it is obviously disadvantageous for production, however.
In view of the above, some improvements have been disclosed later on to mainly introduce a silicon nitride suspension thin-film or chip by micro electromechanical technology, wherein thermistors made by thin-film technology are disposed on the thin-film and undergone laser trimming process for precise control of resistance in the thermistors. The flow-measuring chip is then placed in the flow channel to detect change in the thermistors for flow calculation.
To place the flow-measuring chip in a flow channel may have a high sensitivity to temperature of the fluid, however, it is liable to be affected by the fluid in lifetime, or the flow field may be interfered if it vibrates to incur an incorrect measurement.